Not Applicable
The present invention is related to the field of patient monitoring equipment.
Patient monitoring systems are used in many settings to assist medical personnel in providing care. In many settings, such as hospital wards and nursing homes, there can be problems associated with patients"" getting out of bed without supervision or assistance. A patient may suffer a fall whose effects can range from minor to major. Older patients are at risk of breaking their hips in a fall, requiring extended bed rest and attendant problems. Systems have been known that monitor whether a patient is present in a bed or wheelchair. Essentially, these systems employ a flat sensor laid on the mattress or cushion, and electronic apparatus that responds to signals from the sensor. For example, the strength of a sensor output signal may be proportional to the weight applied to the sensor. The electronic apparatus therefore compares the sensor output signal with one or more predetermined values corresponding to significant thresholds of interest. For example, if the sensor output signal falls below a predetermined low value, the apparatus generates an indication that the patient has gotten out of bed.
Prior patient monitoring systems have used sensors having certain drawbacks that limit performance. One such drawback is size. Sensors to be used on a bed are as wide as the bed, but extend only about a foot in the longitudinal direction. These sensors are intended for placement in the middle of the bed, on the assumption that a patient""s weight is concentrated there. However, a patient may move into a position away from the sensor, resulting in a false alarm. Existing sensors have also employed switches as sensing elements, which can provide only a binary indication. Due to the lack of resolution, only limited information can be obtained from the sensor.
In accordance with the present invention, a sensor-based patient monitoring system is disclosed incorporating features that overcome limitations of the prior art. In addition to having superior performance for traditional uses, such as reducing the incidence of patient falls, the system can be used for a variety of other clinical purposes to assist medical personnel and enhance the quality of care.
The system includes a replaceable laminar sensor placed on a bed or similar surface, the sensor including distributed force sensing elements providing output signals to processing apparatus for processing the force distribution information. The processing apparatus includes a near-bed processor and a central processor coupled to the near-bed processor by a wireless communication link. The processing apparatus applies spatial weighting to the sensor output signals to derive the force distribution across the sensor, and processes the force distribution information over time to generate pertinent patient status information. The information can vary depending on the operational purpose for the monitoring. For example, the information can include patient presence, position, agitation, seizure activity, or respiration. The information can be used to generate a display at a central monitoring station, and to update medical databases coupled to the central processor. The information can also be provided to a paging system to alert attending medical personnel.
The disclosed laminar sensor is made of layers of olefin film having patterns of conductive ink deposited thereon to form capacitive sensing elements, ground planes, and signal traces. The layers are laminated with a foam core selected to provide desired sensitivity of the capacitive sensing elements for a range of expected patient weights. Both a low-cost process and a high-volume process for manufacturing the sensor are shown.
Other aspects, features, and advantages of the present invention are disclosed in the detailed description that follows.